Electric motor control for seriesparallel operation



fipxfi 15, 1947. I 'R. M. STRONG ELECTRIC MOTOR CONTROL FOR SERIES-PARALLEL OPERATION Filed Sept. 18, 1942 WEN EEv'SES:

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Patented Apr. 13, T1947 ELECTRIC MOTOR CONTROL FOR SERIES- PARALLEL OPERATION Robert M. Strong, Wilklnsburg, Pa., assignor to Westinghouse Electric Corporation, East Pltts-' burgh, Pa, a corporation of Pennsylvania Application September 18, 1942, Serial No. 458,895

(or. irz css) 8 (Jlaims.

'* generally, to control syslcularly, to systems for con terns more trolling the operation of Diesel or gas electric locomotives.

On Diesel electric locomotives of certain types the motor connection are changed from series to parallel to obtain full engine loading at high locomotive speeds. The change of connections, commonly known. its-transition, is usually per-= formed automatically by means of a relay set to at a predetermined voltage. However; the transition is performed automatically only when changing the motor connections from series to parallel and not from parallel back to series. Thus, it is necessary to shut off and reapply power, thereby changing from parallel to series, whenever an upgrade is en countered or for any reason the locomotive is slowed down to a speed below the transition point. Since the parallel connection requires twice the generator current required for the series connection; there is danger of burning out the generarely on the operator to tor by operating above thecontinuous current 1 rating if the operator fails to change the motor connections from parallel to series when operat ing below the proper speed for parallel cpcrationo An object of my invention is to provide for autotactically controlling the transition of electric motors.

Another object of my'invention'is to provide For a fuller understanding of the nature objects of my invention, reference may he one to the Iollowing detailed description, taken in conlunction with the accompanying drawing, in which:

Figure 1 is a diagrammatic view of a control system embodying my invention, and

Fig. 2 is a chart showing the sequence of operation of certain of the switches illustrated in Fig. 1.

Referring to the drawing, the system shown therein comprises a generator ill for supplying current to a plurality of motors l l and 12. which are or a type suitable for propelling a locomotive or other vehicle. The generator H1 is provided with a. field winding l3 which is energised by an exciter I l. The generator l0 and exclter I4 are connected to a common shaft it which may he driven hp. an internal combustion engine (not shown). The exciter I4 is provided with a. self excited field winding l6 and a. separately excited field winding" l! which is energized from a battery l8.

A switch F is provided for connecting the field winding l1 across the battery l8, and a. variable resistor I9 is provided for adjusting the current permitted to flow through the field winding IT. A variable resistor H is provided for adjusting the excitation current in the field winding it of the exciter I l and a variable resistor 22 is provided' for adjusting the excitation current in the for automatic transition from series to parallel and from parallel to series-circuit relation.

A further object of my invention is to provide a simplified and improved system for automath cally controlling the transition of electric mo tors.

A. more general object of my invention is to provide an automatic transition system which shall he simple and efilclent in operation and which may be economically manufactured and installed.

Other objects of my invention will be explained fully hereinafter or will be apparent to those skilled in the art.

in accordance with my invention the transi= tion of the motors of a locomotive from series to parallel-circuit relation is controlled by a relay responsive to the voltage of the generator which supplies current to the motors and the reverse transition from parallel to series-circuit relation is controlled by the same relay in co operation with interlocking members on the switching means for controlling the motor con ncctions.

field winding I3 01 the generator iii. A switch GF is provided for shunting the resistor 22 from the circuit for the field winding l3 during most 0! the operating cycle, as will be explained more fully hereinafter.

In accordance with the usual practice in Dclscl electric locomotives, a switch S is provided for connecting the motors H and ii in series-circuit relation during starting or the train hauled by the locomotive, and switches Pi and P2 are pro vided for connecting the motors in parallehcizm cult relation when the locomotive attains a prc determined speed.

v In order that the transition from series to per allel-circuit relation may be automatically effects ed when the locomotive is operating at the proper speed. a relay Tl is provided for controlling the operation or the transition switches. The relay TI is provided with an actuating coil 23 which is connected across the armature oi the generator it) through a resistor 24. The relay is, therefore, responsive to the generator voltage which, in turn, is proportional to the speed oi the locomotive.

order that the transition from parallel to series-circuit relation may also be automatically controlled, the relay Ti is provided with two sets of contact members 25 and 26 which cooperate with interlock members carried by the transition switches to so control the operation--01 these switches that the motor connectiong-gre changed fromparallel back to series-circuit relation in case the speed of the locomotive, and hence the generator voltage, falls below the normal speed for parallel operation. In this manner, overloading of the generator is prevented, since the reverse transition, as well as the forward transition, are both automatically controlled and are not dependent upon the operator of the locomotive.

The usual throttle controller 21 is provided for controlling the governor setting or the supply of fuel to the engine which drives the generator Ill and exciter H. The controller 21' is provided with contact members 23 which are bridged by a contact member 29 when the throttle controller is actuated to an operating position.

In that the functioning or the foregoing apparatus may be more clearly understood, the operation of the system will now be described in more detail. Assuming that it is desired to apply power to the motors ii and i2 to start the locomotive, the throttle controller 21 is actuated from the idling position to an operating position, thereby increasing the speed of the engine which drives the generator i and exciter i 4.

When the controller 21 is actuated to an operating position. the switches F, GF and S are closed to energize the field windings i1 and l3 0! the exciter i4 and generator 10, respectively, and to connect the motors H and i2 across the generator iii in series-circuit relation.

The energizing circuit for the actuating coil of the switch F may be traced from the positive terminal or the battery i 8 through conductor 3|, the contact members 28 which are bridged by contact member 29 oi the controller 21, conductor 32, the actuating coil or the switch F and conductor 33 to the negative terminal of the battery I8. The energizing circuit for the switch GF extends from the conductor 32 through the contact members or the relay Ti, conductor 34 and the actuating coil of the switch GP to the negative conductor 33.

The energizing circuit for the switch 8 extends from the conductor 32 through an interlock 35 on the switch Pl, conductor 38 and the actuating coil or the switch S to the negative conductor 33.

When the voltage or the generator it, which, as explained hereinbefore, is proportional to the speed or the locomotive, increases sufiiciently to operate the relay Ti, the transition from series to parallel is effected by the closing oi the switch Pi, the opening of the switch S and the closing of the switch P2. The switch PI is closed immediately upon the operation-oi the relay TI to close its contact members 28, thereby energizing the actuating coil of the switch Pl through a circuit which may be traced from the previously energized conductor 32, through the contact members 28, conductor 31 and the actuating coil of the switch Pl to the negative conductor 33.

The closing of the switch Pi interrupts the energizing circuit for the actuating coil of the switch S by opening the interlock 35, thereby causing the switch S to open. The opening oi the switch S establishes an energizing circuit for the actuating coil of the switch P2 which may be traced from the conductor 32 through an interlock 38 on the switch Pl, conductor 38, interlock H oi the switch S, conductor 42 and the actuating coil of the 4 switch P2 to the negative conductor II. The closing or the switch P2 completes the transition from series to parallel.

It will be noted that the energizing circuit for the actuating coil of the switch (31" is interrupted by the operation 01' the relay TI to open its contact members 25. In this manner the switch G1" is opened to insert the resistor 22 in the circuit for the field winding ll of the generator l0, thereby reducing the voltage of the generator during the transition period. Following the completion of the transition, the switch G1" is reclosed by the energization 01' its actuating coil through a circuit which extends from the conductor 32, through an interlock 43 on the switch P2, to conductor II, and hence through the actuating coil of the. switch GP to the negative conductor 33. Accordingly, full-ileld excitation is applied to the gener ator Ill immediately upon the completion oi the transition oi the motors II and I2 from series to parallel-circuit relation.

The reverse transition from parallel to series circuit-relation is automatically eiiected by the operation of the relay TI to open its contact memgg bers 26 and reclose its contact members 23 upon a reduction of the generator volta e as a result of a decrease in the speed or the locomotive or an overloading oi the generator. The opening of the contact members 26 of the relay Tl deenergizes the actuating coil of the switch Pl thereby opening this switch. Following the opening of the switch PI the switch 5 is closed by the energization oi its actuating coil through the interlock 35 carried by the switch PI. The closin! of the switch S interrupts the energizing circuit for the actuating coil or the switch P2 by the opening or the interlock 4| carried by the switch 5. It will be noted that the switch P2 remains closed until after the switch 8 is closed, since its actuating coil remains energized through a circuit provided by interlock 44 which is connected in parallel circuit-relation to the interlock ll on the switch PI. Therefore, at least one of the motors is always connected across the generator during the transition period and at no time is the tractive effort entirely lost.

From the foregoing description, it is apparent that I have provided a system for automatically controlling the transition or electric motors from series to parallel circuit-relation and from parallel back to series-circuit relation, which is extremely simple and requires a relatively small amount of equipment. The automatic operation is controlled by one relay in cooperation with a few interlocks which are standard equipment on switches of the type utilized for controlling the motor connections on an electrically propelled vehicle. Accordingly the present system avoids the 'use of several 01' the relays previously required in automatic transition systems or the present type. Therefore, it is apparent that the present system may be readily applied to any locomotive or other vehicle or the type herein described.

I do not desire to be restricted to the particular form or arrangement of parts herein shown and described, since it is evident that they may be changed and modified without departing from the spirit and scope of my invention as defined in the appendedclaims.

I claim as my invention:

1. In a control system, in combination, a plurality 0! electric motors, a generator for supplying current to the motors, a switch for connecting the motors in series-circuit relation. additicnei switches for connecting the motors in paralie circuit relation, said switches being separately operable in sequential relation, interlock- "the motors in series-circuit relation, additional switches for connecting the motors in parallelcircuit relation, said switches being separately operahle in sequential relation, interlocking means actuated by said switches for controlling the sequence of operation of said switches, and a single relay responsive solely to the generator voltage and cooperating with said interlocking means to control the transition of the motors from series to parallel and from parallel to series-circuit reiation that at least one of said motors is always connected to the generator during the transition periods.

In a control system, in combination, a plurality of electric motors, a generator for supplying current to the motors, a switch for connecting the motors in series-circuit relation, a controller for controlling the operation of said switch, additional switches for connecting the motors in paraliel-circuit relation, said switches being separately operable in sequential relation, interlocking means actuated by said switches for controlline" the sequence of operation or said switches, and a single relay responsive solely to the generator voltage and cooperating with said interlocking means to so control the transition of the motors from parallel to series-circuit relation that at least one of said motors is always connected to the generator during the transition period.

4. In a control system, in combination, a plurality of electric motors, a generator for supplying current to the motors, a switch for connecting the motors in series-circuit relation, a controller for controlling the operation of said switch, additional switches for connecting the motors in parallehcircuit relation, said switches being separately operable in sequential relation, interlocking means actuated by said switches for control-' ling the sequence of operation of said switches, and a single relay responsive solely to the generator voltage and cooperating with said interlockins means to so control the transition of the motors from series to parallel and from parallel to series-circuit relation that at least one of said motors is always connected to the generator during the transition periods.

5, in a control system, in combination. a plurality of electric motors, a generator for supplymg current to the motors, means for varying the generator excitation, a switch for connecting the motors in series-circuit relation, 8. controller for controlling the operation or said switch, additional switches for connecting the motors in par--v allel-circuit relation, said switches being separately operable in sequential relation, interlockmg means actuated by said switches for controlthe sequence of operation of said switches,

a single voltage a means to c from series to circuit relation that at always cone L transition means on the s to control the op means to reduce or parallel to series t one of said motors tn tne relay .oeireol switching s to son no relation, and e of said gener ilijl'iiilg means to air erator in some a relay responsi c relation aria ailel to series eirc 7. An electric ternal comhustt orator driven icy rent motors, swito motors to said gene cult relation, said generate: means, said high generator from series to p ping out at p.c age to retransiei; series circuit relation, said relay for reducing ti orator during predate or said motors elation and drc W enerator rolt or parallel as controlled hr orator 0 current motors,

in series or par": '"ela r responsive to the allel circuit rel r controlling evoltage oi switchina means, ,l. up at, p determined. high so "ate-r voltage to tran for said motors from series to parallel circuit relation and dropping out predetermined low senor ator voltage to r said motors from par allel to series c ation, means for rcduo-= generator, means 1. effecting operation of during said transfer lied lay said switching "old reducing means ope a which? Sl' @NG.

of record in the controlled by" sale said field reducing me operation, and in means for rende Number 2,264,853 r 0. Dec, 2, lilo-l 2,266,326 'lliiliruist .u Dec, iii, 1242i 2,292,203 Cowin Aug, 4, 1942 1,871,472 Sawyer as .M dug, in, 1e32, 2,056,783 Frans u ml. Oct. ii, W36 1,860,523 Wmm a May ti, 

